AastraAsterisk: update AMI functions
Split the send_request function so we can send a request without waiting, add
Hangup and PlayDTMF events, allow specification of the event mask, really set
the timeout on the listen streams, add a timed wait_event() function which
waits for either an event or the timeout.
Signed-off-by: James Bottomley <JBottomley@Parallels.com>